A scanner (generally, also referred to as an image reading apparatus) which reads an image of a document is known. Also, a scanner (hereinafter, also referred to as an “ADF scanner”), equipped with auto document feeder (ADF), which reads images of a plurality of documents, while sequentially conveying the plurality of documents to be read, is known.
Prior to reading a document while conveying it, the ADF scanner detects a size of the document. One of its purposes is to detect a document jam. Document jam refers to a failure of a conveyance mechanism for conveying a document along a conveying path, which is also known as a manuscript jam or a paper jam. Occurrence of a document jam may cause folding or tearing of the document. A scanner can detect a document jam, based on a size of the document conveyed and a conveyance distance of the document.
Patent Literature (PTL) 1 discloses a technique of receiving light reflected by an edge of the document conveyed, thereby detecting the edge of the document using a document read sensor.